I posted this in the Scrapbook and not in IMA status, because I could not find an "official" reference yet (Admins feel free to move this thread!).

I don't know about the policy of Mindat regarding the publication of new mineral names, but the lid seems to be off, because at the Munich show this mineral was offered by at least 3 different dealers under its name and not only its IMA number.

Victor N. Yakovenchuk is noted in the IMA list as author. Maybe somebody could get a comment from him.

Ellingsenite is named after the 80 year old amateurgeologist, dr.ing. Hans Vidar Ellingsen, Oslo and the first member of Stenvennerne - Københavns Amatørgeologiske Forening with a mineral named after. We are very proud of Hans Vidar and his wife Astrid.

Abstract:Ellingsenite, Na5Ca6Si18O38(OH)13·6H2O, is a new calcium silicate hydrate (CSH) P-1, a 9.55(3), b 9.395(8), c 16.329(3) Å, α 100.2(1), β 94.9(2), γ 117.8(2)°, V 1251(8) Å3, Z = 1 (from powder-diffraction data) or a 9.576(11), b 9.577(11), c 16.438(19) Å, α 85.85(2), β 75.23(2), γ 60.142(14)°, V 1262(3) Å3, Z = 1 (from single-crystal diffraction data)>, chemically and structurally related to minerals of the gyrolite–reyerite group. The mineral is found in a hydrothermally altered phonolite of the Aris alkaline complex, in Namibia, as snow-white spherules (up to 3 mm in diameter) of well-shaped rhomb-like crystals associated with aegirine, albite, manganoneptunite, microcline, natrolite and polylithionite. The mineral is transparent, colorless in separate crystals, white in aggregates, with a vitreous (separate crystals) to silky (aggregates) luster and a white streak. Cleavage is perfect on {001}, and the fracture is smooth. The Mohs hardness is 4. In transmitted light, the mineral is colorless; dispersion is not observed. Ellingsenite is biaxial (–): α 1.520(2), β 1.534(2), γ 1.536 (589 nm), 2Vmeas 5°. Optical orientation: X = c. Dcalc = 2.38 g cm−3, Dmeas = 2.32(5) g cm−3. The mean chemical composition determined by electron microprobe is: Na2O 9.26, K2O 0.23, CaO 17.35, SiO2 60.35, H2O 12.5 (Penfield method), for a total of 99.69 wt.%. The empirical formula calculated on the basis of 57 atoms of oxygen is (Na4.95K0.09)∑5.04(Ca5.57Na0.43)∑6.00Si18.10O38(OH)13·6H2O. The simplified formula is Na5Ca6Si18O38(OH)13·6H2O. The mineral does not effervesce in 1:1 HCl at room temperature. The strongest X-ray powder-diffraction lines <d in Å(I)hkl> are: 15.50(100)001, 4.22(16)2-01, 3.159(30)005, 3.023(33)32-1, 2.791(24)2-1-4, and 1.827(27)5-11. The crystal-structure model of ellingsenite (R1 = 0.247) obtained from a crystal of poor quality displays layers of octahedra and tetrahedra of the T2OT-2 type with the composition {Na1.90Ca5.10X2}, where X = O, OH, with the interlayer content unresolved. Ellingsenite can be considered as a derivative of martinite, obtained from the latter by intercalation of some additional species (most probably, Na hydrosilicate) in between the adjacent layers of octahedra and tetrahedra. The principal absorption bands in the infrared spectrum include 3460, 1600, 1360 and 1025 cm−1 (shoulder at 1140 cm−1) plus four bands in the region of 780–380 cm−1. The mineral is named in honor of Dr. Hans Vidar Ellingsen (born 1930), a well-known Norwegian mineral collector, who found this mineral during his expedition to the Aris complex.

The R-value of the crystal-structure determination (24.7%) explains why it took so long to get this mineral approved.Although ellingsenite crystals generally look fine, they invariably show a horrible crystal quality ...

I have been perusing several flats of Aris material collected by David Shannon in 1995. Using Mindat images as a guide am I correct in assuming that ellingsenite is common? I am finding lots of late white, silky-lustered tiny xls, which I assume are ellingsenite. Sometimes they are sprinkled on/amongst tuppersuatsiaite xls. Suggestions?

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